A variety of equipment such as ship's boilers, stationary electrical power generation plants and other heat exchangers employ numerous tubes through which pressurized fluid passes. An important aspect of the construction and maintenance of such equipment is testing for leaks. Leaks can occur in the tubes themselves or in the joints formed, usually by swaging, between the tubes and the tube sheets that the tubes pass through.
A common practice in testing for leaks is to pressurize the entire system and then inspect for escaping fluid. This approach, however, is problematic. With all tubes and joints pressurized at once, it can be difficult to be certain of the exact source of leaking fluid. Moreover, starting up and pressurizing the entire system for test purposes can be costly and time-consuming. In some situations it is desired to test a partially completed system that cannot be fully pressurized because it is not yet operational.
One solution to the problem of testing an individual joint is described in the inventor's earlier U.S. Pat. No. 4,382,379. However, that apparatus can be used only with a relatively short tube, both ends of which are accessible. It is useful primarily for testing joint forming procedures using short lengths of tube.
Other leak testing apparatus are known in which a cable extends through a tube to anchor the apparatus. In addition, there are radially expandable tube plugs that can be used in combination with test apparatus. However, none of these known devices and techniques have proven entirely satisfactory, especially when used with large heat exchangers and high pressures.
Accordingly, there is a need for an improved apparatus for leakage testing that overcomes disadvantages associated with previously known apparatus and techniques.